Damper position adjusting device and combustion apparatus equipped with the same

ABSTRACT

Provided is a damper position adjusting device allowing adjustment of the position of a damper and capable of detecting any possible rotational abnormality in the damper. The damper position adjusting device is applied to a combustion apparatus such as a boiler  1 , and is provided for a damper  8  for adjusting the amount of air supplied to a burner  2  of the combustion apparatus. The damper position adjusting device is equipped with a stepping motor  23  for rotating the damper  8  about a rotation axis  9  thereof, a detected plate  33  provided so as to be capable of rotating integrally with the rotation axis  9  of the damper  8 , a detector  34  for detecting a slit  35  formed in the detected plate  33 , and a controller  49 . The controller  49  controls the stepping motor  23  such that the damper  8  stops at a specified rotation stop position, and detects rotational abnormality in the damper  8  based on a control signal composed of a drive pulse supplied to the stepping motor  23  and a detection signal composed of a detection pulse obtained through detection of the slit  35  by the detector  34.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a damper position adjusting device for adjusting the amount of air supplied to the burner of a combustion apparatus, and to a combustion apparatus equipped with this damper position adjusting device. In particular, the present invention relates to a damper position adjusting device for adjusting the degree of opening of a damper provided in an air supply path of a boiler of the type in which a gas or an oil is burned, for the purpose of adjusting the flow rate of combustion air supplied to the burner of the boiler, and to a boiler equipped with this damper position adjusting device.

2. Description of the Related Art

In an air supply path for supplying air to the burner of a boiler, there is provided a damper for adjusting an air supply amount. As disclosed in JP 08-303759 A, in a known conventional damper, one of two positions, that is, a high combustion air volume position and a low combustion air volume position, is selectively assumed.

In the invention as disclosed in JP 08-303759 A mentioned above, the position at which the damper is to be stopped is selected only between two positions. However, with such selective control alone, it is impossible to adjust a damper position based on changes in an outside air temperature, etc. Further, there are limitations regarding an improvement in terms of combustion state, fuel efficiency and the like. Even if the damper position is adjusted by using a stepping motor, there is a fear in that rotational abnormality may occur due to an excessive load. That is, it can happen that, although a rotation drive pulse has been output to the stepping motor, the stepping motor does not actually rotate and, by extension, the damper does not rotate, resulting in a rotation defect such as generation of black smoke. Thus, some measures must be taken to prevent such rotational abnormality.

Further, in the invention as disclosed in JP 08-303759 A, in which the damper stop position is just controlled in an either/or fashion, it is naturally impossible to adjust the damper position based on the exhaust gas temperature. Further, it is impossible to adjust the damper position based on changes in the amount of dust, the amount of nitrogen oxide, the amount of oxygen, or the amount of carbon monoxide in the exhaust gas, which also means limitations regarding an improvement in terms of combustion state and fuel efficiency.

SUMMARY OF THE INVENTION

It is an object of the present invention to realize a damper position adjusting device allowing adjustment of the position of a damper and capable of detecting any possible rotational abnormality in the damper, and a combustion apparatus equipped with such a damper position adjusting device.

It is a further object of the present invention to realize a damper position adjusting device capable of adjusting the position of a damper so as to maintain an optimum combustion state even if there is a change in the temperature of the exhaust gas or even if there is a change in the amount of dust, the amount of nitrogen oxide, the amount of oxygen, the amount of carbon monoxide, etc. in the exhaust gas, and a combustion apparatus equipped with such damper position adjusting device.

The present invention is made in view of the above. In a first aspect of the present invention, there is provided a damper position adjusting device provided in a damper for adjusting an amount of air supplied to a burner of a combustion apparatus, including: a motor for rotating the damper about a rotation axis of the motor; a detected plate provided so as to be capable of rotating integrally with the rotation axis; a detector for detecting a slit formed in the detected plate; and a controller for controlling the motor so that the damper stops at a specified rotation stop position and for detecting any rotational abnormality of the damper based on a control signal supplied to the motor and a detection signal from the detector.

In the first aspect of the present invention, by controlling the motor so as to stop at a specified rotation stop position, it is possible to arbitrarily adjust the rotation stop position of the damper. Further, it is possible to detect any rotational abnormality in the damper based on the control signal supplied to the motor and the detection signal from the detector. That is, it is possible to detect any rotational abnormality in the damper by grasping the actual operation state of the damper through the detection signal from the detector and comparing the actual operation state with the control signal output to the motor.

In a second aspect of the present invention, there is provided a damper position adjusting device according to the first aspect, in which the motor is a stepping motor and the controller detects any rotational abnormality of the damper based on the control signal composed of a drive pulse supplied to the stepping motor and the detection signal composed of a detection pulse obtained through detection of the slit by the detector.

In the second aspect of the present invention, by using a stepping motor, the adjustment of the rotation stop position of the damper can be easily effected. Further, it is possible to easily detect any rotational abnormality in the damper based on the control signal composed of the drive pulse supplied to the stepping motor and the detection signal composed of the detection pulse from the detector.

In a third aspect of the present invention, there is provided a damper position adjusting device according to the second aspect, in which the detected plate is one of a circular plate member and sector-shaped plate member having a slit formation region in which a large number of the slits are formed at equal circumferential intervals, the controller rotates the motor in one direction until the detector is outside the slit formation region, and then rotates the motor in the reverse direction until the detector detects a slit at the other circumferential end of the slit formation region, using the slit as an origin, and at the origin, at which the detector detects the slit at the other circumferential end of the slit formation region, the damper totally closes an air supply path leading to the burner, and at the position at which the detector detects a slit at one circumferential end of the slit formation region, the damper totally opens the air supply path leading to the burner.

In the third aspect of the invention, there is used a detected plate having a large number of slits in the range from the totally closed position to the totally open position of the damper, and an origin corresponding to the totally closed position is confirmed before use, thereby making it possible to detect any rotational abnormality in the damper with a simple construction and control.

In a fourth aspect of the present invention, there is provided a damper position adjusting device according to any one of the first through third aspects, further including one or a plurality of the following sensors: an outside air temperature sensor for detecting a temperature of the air supplied to the burner; an exhaust gas temperature sensor for detecting a temperature of an exhaust gas of the combustion apparatus; and a dust sensor, a nitrogen oxide sensor, an oxygen sensor, and a carbon monoxide sensor for detecting the amount of dust, nitrogen oxide, oxygen, and carbon monoxide or carbon monoxide in the exhaust gas, respectively, in which the controller adjusts the rotation stop position for the damper based on the output of the sensor(s).

In the fourth aspect of the invention, by using various sensors, it is possible to perform control taking the outside air temperature and the exhaust gas temperature into consideration, and further, to perform control taking the amount of dust, the amount of nitrogen oxide, the amount of oxygen, or the amount of carbon monoxide in the exhaust gas into consideration. As a result, it is possible to effectively prevent a combustion defect without conducting any maintenance.

In a fifth aspect of the present invention, there is provided a damper position adjusting device provided in a damper for adjusting the amount of air supplied to a burner of a combustion apparatus, including: a motor for rotating the damper about a rotation axis of the motor; a sensor for detecting a temperature of an exhaust gas of the combustion apparatus or the amount of dust, nitrogen oxide, oxygen, or carbon monoxide in the exhaust gas; and a controller for adjusting the motor based on a detection signal from the sensor to adjust a rotation stop position for the damper.

In the fifth aspect of the invention, it is possible to perform control taking the exhaust gas temperature into consideration, and further, to perform control taking the amount of dust, the amount of nitrogen oxide, the amount of oxygen, the amount of carbon monoxide, etc. in the exhaust gas into consideration, making it possible to automatically adjust the damper position in response to changes in those amounts to thereby prevent a combustion defect.

In a sixth aspect of the present invention, there is provided a damper position adjusting device according to the fifth aspect, further including one or a plurality of the following sensors: an outside air temperature sensor for detecting a temperature of the air supplied to the burner; an exhaust gas temperature sensor for detecting a temperature of an exhaust gas of the combustion apparatus; and a dust sensor, a nitrogen oxide sensor, an oxygen sensor, and a carbon monoxide sensor for detecting the amount of dust, nitrogen oxide, oxygen, and carbon monoxide or carbon monoxide in the exhaust gas, respectively, in which the controller controls the motor based on a detection signal from the sensor to adjust the rotation stop position for the damper.

In the sixth aspect of the invention, it is possible to perform control taking into consideration a plurality of factors among the temperature of the supplied air, the temperature of the exhaust gas discharged, and the amount of dust, the amount of nitrogen oxide, the amount of oxygen, or the amount of carbon monoxide in the exhaust gas, making it possible to automatically adjust the damper position in response to changes in those factors to thereby prevent a combustion defect.

In a seventh aspect of the present invention, there is provided a damper position adjusting device according to the sixth aspect, in which the controller controls the motor to adjust the rotation stop position for the damper, according to priorities pre-assigned to the plurality of sensors, giving high priority to a detection signal from a sensor of a higher order of priority.

In the seventh aspect of the invention, control is performed according to the assigned priorities given to a plurality of sensors, thereby making it possible to prevent a combustion defect through a simple control.

In an eighth aspect of the present invention, there is provided a damper position adjusting device according to any one of the first through seventh aspects, in which the damper position adjusting device is applicable to an existing combustion apparatus, and the damper position adjusting device is mounted thereto by connecting a drive shaft of the damper position adjusting device driven by the motor to the rotation axis of an existing damper.

In the eighth aspect of the invention, retrofitting of the damper position adjusting device to an existing combustion apparatus is possible. Thus, even in an existing combustion apparatus, it is possible to adjust the damper rotation stop position, and to detect any rotational abnormality in the damper.

In a ninth aspect of the present invention, there is provided a damper position adjusting device according to the eighth aspect, in which a plurality of slit formation regions are formed in the detected plate so as to allow application to a plurality of kinds of combustion apparatus, and a slit formation region corresponding to the combustion apparatus to which the damper position adjusting device is applied is used.

In the ninth aspect of the invention, it is possible to provide a damper position adjusting device as a component having commonality between a plurality of kinds of combustion apparatus.

Further, in a tenth aspect of the present invention, there is provided a combustion apparatus including a damper position adjusting device as described with reference to any one of the first through ninth aspects.

In the tenth aspect of the invention, it is possible to provide a combustion apparatus such as a boiler, providing the effect of any one of the first through ninth aspects.

In the damper position adjusting device of the present invention and the combustion apparatus equipped therewith, it is possible to adjust the damper position, and further, to detect any possible rotational abnormality in the damper. If any such rotational abnormality should be detected, it is possible to prevent operation in a defective combustion state by, for example, stopping combustion in the combustion apparatus.

Further, in the damper position adjusting device of the present invention and the combustion apparatus equipped therewith, it is possible to maintain an optimum combustion state through adjustment of the damper position even if there is a change in the exhaust gas temperature, or in the amount of dust, nitrogen oxide, oxygen, carbon monoxide, etc. in the exhaust gas.

Next, an embodiment of the present invention will be described.

The damper position adjusting device of the present invention is applicable to various kinds of combustion apparatus (thermal components) such as a water tube boiler like a small once-through boiler, a water heater, and the reheater of an absorption-refrigerator. Such combustion apparatuses have, in addition to a burner, an endothermic member group heated through combustion of this burner. Further, the combustion apparatus has, in an air supply path for supplying combustion air to the burner, a damper which can adjust the flow rate of the air supplied. This damper is a valve provided in the air supply path, and composed of a plate member rotatable about a rotation axis. Thus, by adjusting the rotation stop position of the damper, it is possible to adjust the flow rate of the air supplied to the burner.

The damper position adjusting device is a device adapted to move the rotation axis of the damper so as to allow adjustment. The damper position adjusting device is equipped with a drive shaft connected to the rotation axis of the damper, rotating the drive shaft by a motor that allows arbitrary adjustment of the rotation stop position. As a result, the rotation stop position of the rotation axis and, by extension, of the damper is adjusted. Typically, a stepping motor (pulse motor) is used as the motor.

To detect any rotational abnormality in the stepping motor, the damper position adjusting device is equipped with a detected plate provided so as to be rotatable integrally with the rotation axis of the damper, and a detector for detecting a slit formed in the detected plate.

The detected plate is a plate member provided so as to rotate integrally with the drive shaft. Typically, the detected plate is composed of a disc. At least in a part of the outer peripheral portion of this disc, there are formed a large number of slits at equal circumferential intervals to constitute a slit formation region. The slits are arranged to extend in the radial direction of the disc, and are of the same configuration and size. Those slits are formed as thin and narrow rectangular grooves or holes extending through an opaque disc formed of metal or the like. Alternatively, printing may be performed on a transparent disc formed of plastic or the like so as to form alternate dark and light circumferential stripes, using the resultant transparent portions as the slits. Instead of being formed as a circular disc, the detected plate may also be formed as a sector-shaped member as long as it has the slit formation region.

The detector is fixed to the outer case, etc. of the damper position adjusting device, and is equipped with a light emitting element and a light receiving element. Typically, the detector is possible to use a photo interrupter. The detector is mounted, with the detection plate interposed between the light emitting element and the light receiving element thereof. That is, the detected plate is provided so as to rotate with the drive shaft and, by extension, with the damper, with the outer peripheral portion thereof being arranged between the light emitting element and the light receiving element of the detector.

When the damper rotates between the totally closed position and the totally open position of the air supply path, the detected plate also rotates integrally with the rotation axis of the damper. The slit formation region is the region of the detected plate which passes the detector in this process. In this embodiment, the damper position adjusting device is mounted to the rotation axis of the damper such that the position where the detector detects the slit at one circumferential end of the slit formation region corresponds to the totally open position of the damper, and that the position where the detector detects the slit at the other circumferential end of the slit formation region corresponds to the totally closed position of the damper.

The damper position adjusting device is controlled by a controller as a control device. This controller obtains detection signals corresponding to the slits from the detector. Thus, when the detector is within the slit formation region of the detected plate, the slits are detected at predetermined intervals as the motor and, by extension, the damper rotates. Conversely, when the detector is outside the slit formation region, no slit is detected even when the motor and, by extension, the damper rotates. By utilizing this phenomenon, the controller is capable of performing origin confirmation of the damper position. To be more specific, the origin is confirmed as follows. The motor is rotated in one direction until the detector is placed outside the slit formation region, and then reversed until the slit at the other circumferential end of the slit formation region is detected. The position thus reached should serve as the origin.

The controller controls the motor such that the drive shaft stops at a specified rotation stop position. When a stepping motor is used as in this embodiment, by supplying a control signal composed of a drive pulse to the stepping motor, it is possible to cause the motor and, by extension, the damper to make normal or reverse rotation by a desired angle.

The controller outputs a control signal to the motor in order to drive the motor by a desired amount. Based on this control signal, it is checked whether the damper has been actually opened/closed by a desired amount or not. That is, the controller monitors the damper for any rotational abnormality by comparing the detection signal from the detector with the control signal supplied to the motor. When a stepping motor is used as in this embodiment, a control signal composed of a drive pulse supplied to the stepping motor and a detection signal composed of a slit detection pulse obtained by the detector are compared with each other to thereby check whether any rotational abnormality exists or not.

For example, when no detection pulse from the detector is detected although a drive pulse has been supplied to the stepping motor, it is judged that there is some rotational abnormality, and the combustion in the boiler is stopped. Conversely, also when a pulse from the detector is detected although no drive pulse has been supplied to the stepping motor, it is possible to cause the device to judge that there is some rotational abnormality.

The damper position adjusting device may be equipped with one or a plurality of sensors selected from among the following group: an outside air temperature sensor for detecting the temperature of the air supplied to the burner; an exhaust gas temperature sensor for detecting the temperature of the exhaust gas of the combustion apparatus, and a dust sensor; a nitrogen monoxide sensor, an oxygen sensor, and a carbon monoxide sensor for detecting the amount of dust, nitrogen oxide, oxygen, or carbon monoxide, respectively. In this case, by using those sensors, it is possible to perform control taking into consideration the outside air temperature, the exhaust gas temperature, and the amount of dust, the amount of nitrogen oxide, the amount of oxygen, or the amount of carbon monoxide in the exhaust gas.

For example, when an outside air temperature sensor is provided, it is possible to adjust the rotation stop position based on the output of the outside air temperature sensor. Thus, it is possible, for example, to adjust the air ratio of the air supplied to the burner, and to continue operation with a fixed air ratio without depending on the outside air temperature. Here, the term air ratio means (actual combustion air amount)/(theoretical combustion air amount). That is, the term “air ratio” is defined as “the actually required amount of air for combustion” “the theoretically required amount of air for combustion”. The air undergoes a change in volume as the outside air temperature changes. By providing the outside air temperature, it is possible to easily cope with this change in volume.

In a combustion apparatus such as a boiler, the damper position adjusting device according to this embodiment is mounted to the rotation axis of the damper provided in the air supply path leading to the burner of the combustion apparatus. By controlling the motor, the damper can also totally close the air supply path at the time of combustion stop, making it possible to prevent air or gas from flowing backward from the boiler body (furnace) to the air supply path. Thus, it is possible to minimize the thermal influence on the duct and various apparatuses connected to the duct, and to prevent heat exhaust loss due to draft. In particular, it proves effective for an ignition system using a pilot burner, making it possible to adjust the air supply amount, etc. at the time of pilot combustion.

Further, the opening/closing control of the damper by the controller can be adjusted based on the outputs of various sensors. There are no particular limitations regarding the kind of sensor used. One or a plurality of sensors are selected for use from among the following group: an outside air temperature sensor for detecting the temperature of the air supplied to a burner; an exhaust gas temperature sensor for detecting the temperature of the exhaust gas of a combustion apparatus; a dust sensor for detecting the amount (concentration) of dust in the exhaust gas; a nitrogen oxide sensor for detecting the amount (concentration) of nitrogen oxide in the exhaust gas; an oxygen sensor for detecting the amount (concentration) of oxygen in the exhaust gas; a carbon monoxide sensor for detecting the amount (concentration) of carbon monoxide in the exhaust gas, etc. The mounting positions of the sensors are determined as appropriate. The outside air temperature sensor can be provided in the air supply path, etc., and the exhaust gas temperature sensor, the dust sensor, the nitrogen oxide sensor, the oxygen sensor, and the carbon monoxide sensor are provided in the exhaust gas passage (chimney).

When the combustion apparatus is a boiler, the controller controls the motor so as to switch the damper between a low combustion air volume position and a high combustion air volume position according to the operation process thereof, adjusting each of the above positions based on detection signals from the various sensors mentioned above. This makes it possible to perform control taking into consideration the outside air temperature, the exhaust gas temperature, the dust amount, the amount of nitrogen oxide, the amount of oxygen, or the amount of carbon monoxide in the exhaust gas.

For example, as stated above, the air undergoes a change in volume as the outside air temperature changes. However, when an outside air temperature sensor is provided, it is possible to easily cope with this change in volume.

When a dust sensor is used, the damper is adjusted so as to reduce the amount of dust. When a nitrogen oxide sensor or a carbon monoxide sensor is used, the damper is adjusted so as to reduce the amount of nitrogen oxide or carbon monoxide. When an oxygen sensor is used, the damper is adjusted so as to maintain an oxygen concentration for optimum combustion state, or, as in the case of the outside air temperature sensor, the damper is adjusted so as to set the air ratio to a fixed level. In the case of an exhaust gas temperature sensor, the damper is adjusted so as to attain an optimum combustion state based on the exhaust gas temperature.

It is possible to use only one of those sensors for control, or to use a plurality of sensors in a combination to adjust the damper. When a plurality of sensors are used, control can be performed according to pre-set degrees of priority, giving high priority to a detection signal from a sensor of a higher order of priority.

The damper position adjusting device can be of a construction allowing retrofitting to the rotation axis of an existing damper of an existing combustion apparatus. Combustion apparatuses, such as boilers, can be classified into two types: one in which the damper is opened through clockwise rotation and one in which the damper is opened through counterclockwise rotation. Further, the structure of the key groove of the rotation axis of the damper may be of different types with respect to the damper plate surface according to the combustion apparatus model. To allow common application of the damper position adjusting device to combustion apparatuses of those different types, a plurality of slit formation regions may be provided in the detection plate. In this case, one of the slit formation regions is selectively used according to the combustion apparatus to which the damper position adjusting device is applied.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic longitudinal sectional view of a boiler to which a damper position adjusting device according to the present invention is applied;

FIG. 2 is a sectional view taken along the line II-II of FIG. 1;

FIG. 3 is a perspective view of a main body portion of a damper position adjusting device according to an embodiment of the present invention;

FIG. 4 is a schematic view, partly in section, showing how the damper position adjusting device of FIG. 3 is used and how control is effected;

FIG. 5 is a sectional view of a rotational abnormality detecting device and a damper position indicating device of the damper position adjusting device of FIG. 3; and

FIG. 6 is a diagram showing a modification example of a detected plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, a specific example of the present invention will be described in detail with reference to the drawings. While the damper position adjusting device of the present invention is applicable not only to a boiler but also to the reheater of an absorption-type refrigerator, etc., the example described below is applied to a once-through-type steam boiler, which is a kind water tube boiler.

FIG. 1 is a schematic longitudinal sectional view of a boiler to which an example of the damper position adjusting device of the present invention is applied. FIG. 2 is a sectional view taken along the line II-II of FIG. 1.

A boiler 1 according to this example is equipped with a burner 2 and a boiler body 4 in which a large number of heat transfer tubes 3 are arranged. The burner 2 is provided at one end of the boiler body 4. This example adopts a completely premixed type burner having a flat combustion surface (premixed gas ejection surface). The boiler body 4 has, on one side thereof, that is, on the burner 2 side, an air supply path 6 for sending combustion air from a blower 5 to the burner 2, and on the other end thereof opposite to the burner 2, an exhaust gas passage (chimney) 7 for discharging exhaust gas from the boiler body 4. The air supply path 6 has, on the downstream side of the blower 5, a damper 8 for adjusting the amount of air supplied to the burner 2. The damper 8 is a plate member rotatable about a rotation axis 9 arranged so as to be orthogonal to the flow passage direction of the air supply path 6. The damper 8 is rotatably retained inside a duct (with no reference numeral) constituting the air supply path 6. As a result, the rotating angle thereof is adjusted, making it possible to adjust the amount of air sent to the burner 2.

In the air supply path 6, there is further provided, on the downstream side of the damper 8, a gas fuel supply tube 10 for injecting a fuel gas into the air supply path 6. The fuel gas is injected into the air supply path 6 through the gas fuel supply tube 10, thereby making it possible to mix the fuel gas into the air supplied to the burner 2. The gas fuel supply tube 10 is equipped with a fuel flow rate adjustment valve 11, making it possible to adjust the flow rate of fuel gas injected.

The heat transfer tubes 3 provided inside the boiler body 4 are arranged between an upper header 12 and a lower header 13. Further, as shown in FIG. 2, outer heat transfer tubes 14 arranged along both side walls of the boiler body 4 are connected together by plate-like portions 15 to form water tube walls 16. Between the pair of water tube walls 16, the upper header 12, and the lower header 13, the combustion gas generated through combustion at the burner 2 is guided so as to flow linearly toward the exhaust gas passage 7.

The damper 8 in the air supply path 6 is provided with a damper position adjusting device according to the present invention. The damper position adjusting device of this example is installed on the outer surface of the duct (not indicated by reference numeral) constituting the air supply path 6, and operates the rotation axis 9 of the damper 8, thereby changing the degree of opening of the air supply path 6 defined by the damper 8 to adjust the flow rate of the combustion air.

FIGS. 3 through 5 are diagrams each showing a damper position adjusting device 17 according to this example, of which FIG. 3 is a perspective view of a main body portion 18, FIG. 4 is a schematic system view, partly in section, showing how the device is used, and FIG. 5 is a sectional view of a rotational abnormality detecting device 19 and a damper position indicating device 20.

The damper position adjusting device 17 of this example is equipped with a drive shaft 21 detachably connected to the rotation axis 9 of the damper 8, and the drive shaft 21 can be rotated by a motor 23 through the intermediation of a reduction gear 22. As the motor 23, a motor is used which allows arbitrary adjustment of the rotation stop position. In this example, a stepping motor (pulse motor) 23 is used.

The drive shaft 21 is connected to the rotation axis 9 of the damper 8 through the intermediation of a coupling 24 so as to allow coaxial, integral rotation. The coupling 24 of this example is formed as a stepped cylinder having at its center a stepped small diameter hole 25 and a stepped large diameter hole 26 both extending therethrough in the axial direction. The drive shaft 21 is inserted into the small diameter hole 25, and is integrated with the coupling 24 by a mounting screw 27. On the other hand, the rotation axis 9 of the damper 8 can be inserted into the large diameter hole 26, and is allowed to make integral rotation with the coupling 24 by means of a key 28. For this purpose, key grooves 29 and 30 are formed in the rotation axis 9 and the large diameter hole 26 of the coupling 24, respectively.

With the drive shaft 21 inserted into one end portion of the coupling 24, the other end portion of the coupling 24 is rotatably retained by an outer case 32 of the damper position adjusting device 17 through the intermedition of a bearing 31. In the outer case 32, the coupling 24, the rotational abnormality detecting device 19, etc. are sealed, with the reduction gear 22 and the stepping motor 23 being retained at one end thereof and the large diameter hole 26 of the coupling 24 being exposed at the other end thereof.

The rotational abnormality detecting device 19 is equipped with a detected plate 33 and a detector 34. The detected plate 33 is fixed to the stepped portion at the axial center of the coupling 24 so as to extend radially outwards. The detected plate 33 of this example is composed of a thin disc which is formed of a metal such as stainless steel. The detected plate 33 is provided coaxially with the coupling 24 and the drive shaft 21. In a part of the outer peripheral portion of the detected plate 33, there is provided a slit formation region 36 in which a large number of slits 35 are formed at equal circumferential intervals. In this example, the slit formation region 36 covers a quarter (90 degrees) of the circumference. The slits 35 formed in the slit formation region 36 are of the same configuration and size. In this example, thin and narrow rectangular grooves extending in the radial direction of the detected plate 33 are formed by stamping at equal circumferential intervals.

The detector 34 for detecting the slits 35 is fixed to the outer case 32. The detector 34 of this example is composed of a transmission type photo interrupter, which is mounted such that the outer peripheral portion of the detected plate 33 is situated between a light emitting element 37 and a light receiving element 38. With the arrangement in which the detected plate 33 exists between the light emitting element 37 and the light receiving element 38 of the detector 34, switching is effected between reception and non-reception of light from the light emitting element 37 by the light receiving element 38 depending upon whether a slit 35 is situated at a position corresponding to the detector 34 (the position corresponding to the optical path from the light emitting element 37 to the light receiving element 38). In this way, the detector 34 can detect the slits 35 formed in the detected plate 33.

In mounting the damper position adjusting device 17 to the rotation axis 9 of the damper 8, positioning is effected such that the damper 8 totally closes the air supply path 6 when a clockwise-end slit 39 of the slit formation region 36, shown in FIG. 5, is at the position corresponding to the detector 34. The position of the key groove 29 of the rotation axis 9 with respect to the plate surface of the damper 8 is previously determined, so the above-mentioned positioning can be easily effected by adjusting in advance the circumferential position of the key groove 30 formed in the coupling 24 and the circumferential position of the detected plate 33 mounted to the coupling 24.

In this example, the slit formation region 36 is formed so as to cover a range corresponding to 90 degrees of the detected plate 33, so, as stated above, in the state in which the clockwise-end slit 39 of the slit formation region 36 is situated at the position corresponding to the detector 34, the damper 8 totally closes the air supply path 6, whereas, in the state in which the counterclockwise-end slit 40 of the slit formation region 36 is situated at the position corresponding to the detector 34, the damper 8 totally opens the air supply path 6.

The damper position adjusting device 17 (the main body portion 18), constructed as described above, is provided on the outer surface of the duct (with no reference numeral) constituting the air supply path 6. In this regard, the drive shaft 21 is connected to the rotation axis 9 of the damper 8 extending through the duct to the exterior, through the intermediation of the coupling 24. With this construction, the damper position adjusting device 17 of this example easily allows retrofitting to an existing boiler 1 as well.

It is desirable for the position of the damper 8 to allow easy visual recognition by the person performing maintenance on the boiler 1. In view of this, the damper position adjusting device 17 of this example is equipped with the damper position indicating device 20 for indicating the rotating position of the damper 8. The damper position indicating device 20 of this example is equipped with a bar-like indicator 41 provided so as to extend radially outwards from the coupling 24, and an indication plate 43 provided in a circumferential groove 42 formed in the outer case 32.

In the example shown, a proximal portion 44 of the indicator 41 is mounted to the outer peripheral surface of the coupling 24. A round-bar-like indicator main body 45 is formed so as to extend outwardly from one end of the proximal portion 44. Formed in the distal end portion of the indicator main body 45 are slopes 46 approaching to each other as they extend toward the distal end. In the state in which the indicator 41 has been mounted to the coupling 24, a linear distal end portion 47, formed by the slopes 46 joining together, extends in the axial direction of the coupling 24. It is desirable to apply a fluorescent paint or the like to the linear distal end portion 47.

The indicator 41 is mounted to the outer peripheral surface of the coupling 24 by means of a fastening screw 48 inserted into a through-hole (with no reference numeral) formed at the center of the proximal portion 44. The distal end portion of the indicator 41 thus fixed to the coupling 24 protrudes into the circumferential groove 42 formed in the outer case 32. The circumferential groove 42 covers an angular range somewhat larger than 90 degrees. Thus, even if rotational abnormality of the damper 8 occurs, further rotation is prevented by the indicator 41 abutting the ends of the circumferential groove 42.

A flexible transparent indication plate 43 is provided on the outer peripheral surface of the outer case 32 so as to cover the circumferential groove 42. The indication plate 43 is transparent, so it is possible to visually recognize the indicator 41 from outside the outer case 32. Thus, it is possible to ascertain the position of the rotation axis 9, that is, of the damper 8, by the way the indicator main body 45 moves. The indication plate 43 of this example has numbers “0” through “9” affixed thereto at equal intervals. When the damper 8 is totally closed, the indicator 41 (the distal end portion 47 of the indicator main body 45) indicates “0”, and when the damper 8 is totally open, the indicator 41 indicates “9”.

The damper position adjusting device 17 of this example is further equipped with a controller (control device) 49. The controller 49 is connected to the stepping motor 23 and the detector 34. As a result, it is possible to control the rotation of the stepping motor 23 while monitoring the damper for rotational abnormality. To control the stepping motor 23, the controller 49 has a circuit for preparing control signals including the drive pulses for the stepping motor 23, and can output the prepared control signals to the stepping motor 23. As a result, it is possible to arbitrarily control the normal and reverse rotation and the rotation angle of the stepping motor 23. Further, by changing the interval of the drive pulses, the rotating speed is controlled.

In actually performing opening/closing control on the damper 8, the controller 49 first performs an origin detecting operation to establish the totally closed position of the damper 8 as the origin. In this example, the detected plate 33 is first rotated counterclockwise as shown in FIG. 5. Assuming that the detector 34 is arranged within the slit formation region 36 of the detected plate 33, the detector 34 periodically detects the slits 35 as the detected plate 33 rotates, with the result that the detection pulses are input to the controller 49 as detection signals. When the detected plate 33 is rotated until the detector 34 is brought to the exterior of the slit formation region 36, pulse detection is no longer effected. When no pulses are detected for a predetermined period of time, the controller 49 judges that the detector 34 is outside the slit formation region 36, and reverses the rotating direction. That is, in this example, the detected plate 33 is reversed clockwise, and the position where the first pulse (the clockwise end slit 39) is detected is to be regarded as the origin. This origin confirmation through clockwise rotation is effected at a speed lower than that of the counterclockwise rotation prior to the switching of the rotating direction.

The origin thus detected corresponds to the totally closed position of the damper 8, so, using this state as a reference, the controller 49 outputs a drive signal to the stepping motor 23, making it possible to perform opening/closing control on the damper 8. As the controller 49 drives the stepping motor 23 to open/close the damper 8, detection signals corresponding to the slits 35 are obtained from the detector 34 as pulses. Thus, the controller 49 compares the detection signals from the detector 34 with the control signals to be supplied to the stepping motor 23, thereby making it possible to monitor the damper 8 for any rotational abnormality. To be more specific, the control signals composed of drive pulses to be supplied to the stepping motor 23 and the detection signals composed of detection pulses obtained through detection of the slits 35 by the detector 34 are compared with each other to thereby effect monitoring to see if there is any rotational abnormality.

For example, when, although drive pulses have been supplied to the stepping motor 23, no detection pulses are detected by the detector 34, it is judged there is rotational abnormality. The frequency of the detection pulses from the detector 34 usually differs from the frequency of the drive pulses to be supplied to the stepping motor 23, so control is performed taking this difference into consideration. For example, control is performed such that it is judged there is rotational abnormality only when, even though a period of time corresponding to a predetermined drive signal pulses has elapsed, not a single detection signal pulse is detected. When it is determined that there is rotational abnormality, the controller 49 supplies, for example, a stop signal SP to the control panel (not shown) of the boiler 1 to stop combustion. Conversely, it is also possible to detect rotational abnormality when, even though no drive pulses have been supplied to the stepping motor 23, a pulse is detected by the detector 34.

To adjust the rotation stop position of the damper 8 based on the temperature of the air supplied to the burner 2 (outside air temperature), the exhaust gas temperature of the boiler 1, the amount (concentration) of dust, nitrogen oxide (NOx), oxygen (O₂), or carbon monoxide (CO), etc., the damper position adjusting device 17 is preferably equipped with various sensors 50, 51. Examples of the sensors include a temperature sensor, a dust sensor, an NOx sensor, an O₂ sensor, and a CO sensor. It is possible to provide only one such sensor or a plurality of kinds of sensors. Each sensor 50, 51 is connected to the controller 49, and a detection signal is input to the controller 49.

In this example, a first sensor 50 is provided on the outer case 32 of the damper position adjusting device 17, and a second sensor 51 is provided in the exhaust gas passage 7 at the outlet of the boiler body 4 of the boiler 1. The first sensor 50 is an outside air temperature sensor composed of a thermistor, whereas the second sensor 51 is composed of one or more sensors selected from among the following sensors: an exhaust gas temperature sensor for measuring the exhaust gas temperature; a dust sensor, an NOx sensor, an O₂ sensor, or a CO sensor for measuring the amount of dust, nitrogen oxide, oxygen, or carbon monoxide in the exhaust gas, respectively.

It should be noted that it is not always necessary to provide both the first sensor 50 and the second sensor 51, and control can be performed using only one of those sensors. The first sensor 50 composed of an outside air temperature sensor measures the outside air temperature, that is, the temperature of the air supplied to the burner 2. It is only necessary for the first sensor 50 to be capable of detecting the outside air temperature, and there are no particular limitations regarding the mounting position thereof. It may also be installed at a position spaced apart from the outer case 32 of the damper position adjusting device 17.

In the following, the operation of the steam boiler 1 equipped with the damper position adjusting device 17 of this example will be schematically described.

Combustion air (outside air) supplied from an outside air intake passage 52 (see FIG. 1) is premixed in the air supply path 6 with the fuel gas supplied from the gas fuel supply tube 10, and the premixed gas thus obtained is injected into the boiler body 4 from the burner 2. In this process, the premixed gas is ignited by an ignition device (not shown) at the burner 2 and then burned. The combustion gas generated as a result of this combustion undergoes heat exchange with the heat transfer tube group 3 in the boiler body 4 to become exhaust gas, which is discharged into the atmosphere through the exhaust gas passage 7. The water in the heat transfer tubes 3 is heated through heat exchange with the combustion gas, and then vaporized. This steam is supplied from a steam extraction device (not shown) connected to the upper header 12 to equipment using steam (not shown).

In operating the boiler 1 of this example, switching is effected between high combustion and low combustion. For this purpose, the damper 8 can be selectively positioned at either a high combustion air volume position or a low combustion air volume position. The position adjustment of the damper 8 is effected by the controller 49 of the damper position adjusting device 17. That is, a selection signal SL for selection between high combustion and low combustion is input to the controller 49 from the boiler 1, and the motor 23 is controlled based on the same to thereby place the damper 8 at a desired rotation stop position. When the motor 23 is a stepping motor, after the above-described origin detecting operation is performed, a predetermined number of pulses corresponding to each category of combustion are output so that the drive shaft 21 may rotate from the origin to a desired rotation stop position. For example, 500 pulses are output to rotate the damper 8 to the high combustion air volume position, and 200 pulses are output to rotate the damper 8 to the low combustion air volume position. The above-mentioned numbers of output pulses are only given by way of example; they naturally vary according to the motor used. As described above, when the damper 8 rotates, it is monitored by the detector 34 for any rotational abnormality.

In this way, the boiler 1 is operated with the damper 8 placed at either the low combustion air volume position or the high combustion air volume position. The rotation stop positions for the damper 8 are adjusted based on the output from the sensors 50, 51. For example, when the outside air temperature sensor (the first sensor) 50 is used, the position of the damper 8 can be adjusted according to the change in outside air temperature as detected thereby. As a result, even when there is a change in outside air temperature, it is possible to operate the boiler 1 in an appropriate combustion state and with appropriate fuel efficiency.

To be more specific, the controller 49 corrects each of the rotation stop positions for high combustion and low combustion based on the output from the outside air temperature sensor 50. That is, the rotation stop position for the damper 8 is adjusted by, for example, increasing or decreasing the number of pulses taking the outside air temperature into consideration. Through control by the controller 49, it is possible to operate the boiler 1 with, for example, the air ratio controlled to be fixed by the damper position adjusting device 17 of this embodiment. To be more specific, the controller 49 stores a program for controlling the rotation of the motor 23 such that the air ratio of the burner 2 is a substantially fixed value even if the outside air temperature changes.

It is also possible to adjust the rotation stop position for the damper 8 by using, instead of or in addition to the outside air temperature sensor 50, the second sensor, which is selected from among the above-mentioned group: a dust sensor; an NOx sensor; an O₂ sensor; a CO sensor, etc. All of the above-mentioned sensors to be used as the second sensor 51 may be well-known conventional sensors. Regarding the dust sensor, it is possible to use a smoke measurement device in which exhaust gas is caused to exist between a light emitting element and a light receiving element and which grasps the smoke concentration from the light reception intensity at the light receiving element. As the smoke measurement device, it is possible to use the device as disclosed in JP 2005-265609A.

When the dust sensor is used, the damper 8 is adjusted so as to reduce the amount of dust. When the Nox sensor or the CO sensor is used, the damper 8 is adjusted so as to reduce the amount of NOx or CO. When the O₂ sensor is used, the damper 8 is adjusted so as to maintain an oxygen concentration for optimum combustion state, or, as in the case of the outside air temperature sensor, adjusts the damper 8 so as to set the air ratio to a fixed level. Further, in the case of the exhaust gas temperature sensor, the damper 8 is adjusted so as to attain an optimum combustion state based on the exhaust gas temperature.

When a plurality of sensors are selected for use from among the dust sensor, the NOx sensor, the O₂ sensor, the CO sensor, etc., it is possible to prepare a program such that control is effected according to priorities previously assigned to the sensors, giving priority to a detection signal from a sensor of a higher priority. This order of priority may be the same throughout the operation process of the boiler 1, or may be changed according to the stage of operation of the boiler 1.

When the combustion in the boiler 1 is to be stopped, the controller 49 drives the damper 8 to place the air supply path 6 in the totally closed state. This makes it possible to prevent back flow of hot air from the interior of the furnace to the air supply path 6, making it possible to minimize the thermal influence. Further, this also leads to suppression of heat exhaust loss.

While in the above-described example the boiler 1 is already equipped with the damper position adjusting device 17 before the shipment of the boiler 1, the damper position adjusting device 17 is devised as follows to allow easy installment in an existing boiler 1. Suppose that the existing boiler 1 is of a construction which allows selective placement at either a high combustion volume position or a low combustion air volume position, no main body portion 18 shown in FIG. 4 is in the existing boiler 1. Instead, a motor unit (not shown) is provided. To attach the damper position adjusting device 17 to the existing boiler 1, the motor unit, etc. are detached to attach the damper position adjusting device 17 instead. In this regard, the position of a fastening screw (not shown) for the mounting to the outer surface of the duct (with no reference numeral) constituting the air supply path 6, is the same for both the motor unit and the damper position adjusting device 17. With this arrangement, the damper position adjusting device 17 can be easily mounted after removing the motor unit, etc.

With the damper position adjusting device 17 of this example, the damper 8 can be stopped at an arbitrary position with high accuracy by using the stepping motor 23. Further, when controlled with a combination of various sensors 50, 51, the boiler 1 can maintain a satisfactory combustion state. In particular, through combustion at a fixed air ratio or oxygen amount by using the outside air temperature sensor 50, etc., it is possible to achieve an improvement in terms of combustion efficiency, which leads to a reduction in fuel cost. Further, rotational abnormality can be detected through the detected plate 33 and the detector 34, so it is possible to prevent a combustion defect due to malfunction of the apparatus.

The damper position adjusting device 17 and the combustion apparatus equipped therewith are not restricted to the construction of the example described above but allows modification as appropriate. For example, while in the above example the detected plate 33 is a disc, it may also be a sector-shaped member or the like as long as it is equipped at least with the slit formation region 36.

Further, as stated above, the damper position adjusting device 17 may be constructed so as to allow retrofitting to an existing rotation axis 9 of an existing damper 8 in an existing boiler 1. In this case, in the existing boiler 1, the position of the damper 8 can be automatically adjusted based on the detection results from the various sensors 50, 51, making it possible to provide a maintenance-free boiler. In contrast, when the damper position adjusting device 17 is mounted to the boiler 1 from the first, it is possible to achieve commonality between the drive shaft 21 thereof and the rotation axis 9 of the damper 8.

As stated above, the damper position adjusting device 17 allows retrofitting to an existing rotation axis 9 of an existing damper 8. It should be noted, however, the damper 8 is opened through clockwise rotation in some existing boilers 1, whereas it is opened through counterclockwise rotation in other existing boilers 1. Further, the structure of the key groove 29 of the rotation axis 9 of the damper 8 with respect to the plate surface of the damper 8 may differ according to the model. To realize a component having compatibility with such different types of boiler 1, it is advisable, as shown in FIG. 6, to provide a plurality of slit formation regions 36, 53 in the detected plate 33, and to make it possible to change the mounting position of the indicator 41 with respect to the coupling 24. In this case, one of the slit formation regions 36, 53 is selectively used according to the boiler 1 to which the device is applied.

FIG. 6 is a diagram showing a detected plate 33 formed as a component compatible with a plurality of types of boiler 1. In the example shown, the two slit formation regions 36, 53 are formed symmetrically, each covering a range corresponding to 90 degrees. The left-hand slit formation region 36 is used when the device is mounted in a boiler 1 in which the damper 8 is opened through clockwise rotation as in the case of the above-described example.

The right-hand slit formation region 53 is used when the device is mounted in a boiler 1 in which the damper 8 is opened through counterclockwise rotation. In this case, origin confirmation for the damper 8 is performed as follows. First, the detected plate 33 is rotated clockwise until the detector 34 comes out of the slit formation region 53. Then, the detected plate 33 is rotated in the reverse direction, that is, counterclockwise, and the position where the first slit (the counterclockwise end slit 54) is detected is to be regarded as the origin. The circumferential position of the key groove 30 with respect to the coupling 24 is determined such that the damper 8 totally closes the air supply path 6 when the detected plate 33 is at that position. It is advisable for the key groove 30 to be formed at a single position in the coupling 24 so that it may allow common use regardless of whether the right-hand slit formation region 36 or left-hand slit formation region 53 is used. In this example, regarding the indicator 41, there are mounting positions respectively corresponding to the slit formation regions 36, 53. That is, the position at which the indicator 41 is fixed to the coupling 24 is changed according to which of the slit formation regions 36, 53 is used.

In the example shown in FIG. 6, the right and left slit formation regions 36, 53 are spaced apart from each other by 40 degrees taking into consideration the fact that the device is applied to a boiler 1 in which the key groove 29 of the rotation axis 9 is deviated by 20 degrees with respect to the direction perpendicular to the plane of the damper 8.

Further, while in the above-described example the slits 35 of the same configuration are formed in the detected plate 33 at equal circumferential intervals, it is also possible to form slits changed in pattern by a predetermined circumferential angle (not shown), thus providing a detected plate (not shown) allowing recognition of an absolute angle by the detector 34. In this case, the origin detecting operation is facilitated. 

1. A damper position adjusting device provided in a damper for adjusting an amount of air supplied to a burner of a combustion apparatus, comprising: a motor for rotating the damper about a rotation axis of the motor; a detected plate provided so as to be capable of rotating integrally with the rotation axis; a detector for detecting a slit formed in the detected plate; and a controller for controlling the motor so that the damper stops at a specified rotation stop position and for detecting any rotational abnormality of the damper based on a control signal supplied to the motor and a detection signal from the detector.
 2. A damper position adjusting device according to claim 1, wherein the motor is a stepping motor, and wherein the controller detects any rotational abnormality of the damper based on the control signal composed of a drive pulse supplied to the stepping motor and the detection signal composed of a detection pulse obtained through detection of the slit by the detector.
 3. A damper position adjusting device according to claim 2, wherein the detected plate is one of a circular plate member and sector-shaped plate member having a slit formation region in which a large number of the slits are formed at equal circumferential intervals, wherein the controller rotates the motor in one direction until the detector is outside the slit formation region, and then rotates the motor in the reverse direction until the detector detects a slit at the other circumferential end of the slit formation region, using the slit as an origin, and wherein at the origin, at which the detector detects the slit at the other circumferential end of the slit formation region, the damper totally closes an air supply path leading to the burner, and at the position at which the detector detects a slit at one circumferential end of the slit formation region, the damper totally opens the air supply path leading to the burner.
 4. A damper position adjusting device according to any one of claims 1 through 3, further comprising one or a plurality of the following sensors: an outside air temperature sensor for detecting a temperature of the air supplied to the burner; an exhaust gas temperature sensor for detecting a temperature of an exhaust gas of the combustion apparatus; and a dust sensor, a nitrogen oxide sensor, an oxygen sensor, and a carbon monoxide sensor for detecting the amount of dust, nitrogen oxide, oxygen, and carbon monoxide or carbon monoxide in the exhaust gas, respectively, wherein the controller adjusts the rotation stop position for the damper based on the output of the sensor(s).
 5. A damper position adjusting device provided in a damper for adjusting the amount of air supplied to a burner of a combustion apparatus, comprising: a motor for rotating the damper about a rotation axis of the motor; a sensor for detecting a temperature of an exhaust gas of the combustion apparatus or the amount of dust, nitrogen oxide, oxygen, or carbon monoxide in the exhaust gas; and a controller for adjusting the motor based on a detection signal from the sensor to adjust a rotation stop position for the damper.
 6. A damper position adjusting device according to claim 5, further comprising one or a plurality of the following sensors: an outside air temperature sensor for detecting a temperature of the air supplied to the burner; an exhaust gas temperature sensor for detecting a temperature of an exhaust gas of the combustion apparatus; and a dust sensor, a nitrogen oxide sensor, an oxygen sensor, and a carbon monoxide sensor for detecting the amount of dust, nitrogen oxide, oxygen, and carbon monoxide or carbon monoxide in the exhaust gas, respectively, wherein the controller controls the motor based on a detection signal from the sensor to adjust the rotation stop position for the damper.
 7. A damper position adjusting device according to claim 6, wherein the controller controls the motor to adjust the rotation stop position for the damper, according to priorities pre-assigned to the plurality of sensors, giving high priority to a detection signal from a sensor of a higher order of priority.
 8. A damper position adjusting device according to any one of claims 1 through 7, wherein the damper position adjusting device is applicable to an existing combustion apparatus, and wherein the damper position adjusting device is mounted thereto by connecting a drive shaft of the damper position adjusting device driven by the motor to the rotation axis of an existing damper.
 9. A damper position adjusting device according to claim 8, wherein a plurality of slit formation regions are formed in the detection plate so as to allow application to a plurality of kinds of combustion apparatus, and wherein a slit formation region corresponding to the combustion apparatus to which the damper position adjusting device is applied is used.
 10. A combustion apparatus comprising a damper position adjusting device as claimed in any one of claims 1 through
 9. 